1. Technical Field
The present invention relates to photovoltaic converter devices and, in particular, to photovoltaic converter devices that use nanoparticles.
2. Related Art
As clean energy sources that contribute to energy conservation and resource saving, solar cells (i.e., photovoltaic converter devices) are being actively developed. Solar cells are electric power devices that use the photo-electromotive force effect to directly convert light energy to electric power. As their structures, various kinds of structures, such as, organic thin film solar cells, dye-sensitized solar cells, solar cells with multi-junction structure, and the like are being investigated. Above all, solar cells that use quantum dots (nanoparticles) are attracting attention as the next-generation solar cells that make it possible in theory to achieve the conversion efficiency higher than 60%.
For example, Published Japanese translation of a PCT application 2007-535806 (Patent Document 1) describes a solar cell having a plurality of crystalline semiconductor material quantum dots that are separated mutually by dielectric material thin layers.
However, with the structure using silicon as the quantum dots that are examined in detail in the above-mentioned Patent Document 1 and silicon oxide as the dielectric material thin layers, it is feared that charge (electrons) cannot be effectively retrieved from the quantum wells. The above-mentioned Patent Document 1 examines that, according to the super lattice structure described therein, mini-bands are formed so that charges (electrons) can be efficiently retrieved.
However, arranging the super lattice structure, a highly advanced technology is necessary to arrange devices with super lattice structure, in other words, quantum dots. Moreover, in order to form mini-bands, variations in the particle size need to be less than 10% for quantum dots of several nm˜several ten nm in diameter, which makes it extremely difficult.